1. Field of the Invention
The present invention relates to a projection display device, and more particularly to a projection display device that is more compactly composed as compared with a conventional device by reducing the total width of a device, that is, the length between the rear of outer case and screen.
2. Description of the Related Art
Generally, a projection display device is a display system where a small image is implemented on a separate plane (screen) in a large screen by magnifying and projecting the small image through an optical lens (optical engine or projection lens).
The configuration of a projection television (hereinafter, a display device) capable of implementing this system will be described in the following.
FIG. 1 is a cross-sectional view illustrating the configuration of the conventional projection display device.
As shown in FIG. 1, the projection display device 1 comprises an optical engine 2 for projecting an electron beam, a projection lens 3 for magnifying and projecting the electron beam projected by the optical engine 2, a reflection mirror 4 for reflecting the electron beam magnified and projected through the projection lens 3 on the full screen of a screen 5, and the screen 5 for realizing an image using the electron beam reflected by the reflection mirror 4.
Here, the optical engine 2 and the projection lens 3 are mounted in a lower cabinet 7 of an outer case 6, the reflection mirror 4 is mounted on the rear of an upper cabinet 8 of the outer case 6 for reflecting the electron beam magnified and projected through the projection lens 3 in the direction of the screen 5, and the screen 5 is mounted on the front of the outer case 6, the direction of which is opposite to the direction of the reflection mirror 4, so as to realize the electron beam reflected by the reflection mirror 4 on the full screen of the screen 5.
The image realization of the projection display device 1 composed like above configuration will be described.
First, when an electron beam for realizing an image is projected by the optical engine 2, the electron beam is magnified by the projection lens 3 mounted on the top of the optical engine 2 and projected to the full surface of the reflection mirror 4 mounted on the rear of the upper cabinet 8 of the outer case 6, and the magnified and projected electron beam is reflected to the full screen of the screen 5 mounted on the front of the outer case 6, the direction of which is opposite to the direction of the reflection mirror 4, by the reflection mechanism of the reflection mirror 4 and realized on the screen 5 as an image.
However, as the optical engine 2 and the projection lens 3 is mounted in the lower cabinet 7 of the outer case 6 in a limited space, the projection angle of the electron beam magnified and projected by the optical engine 2 and the projection lens 3 has a limitation in a range.
Like this, since the projection angle of the electron beam is limited in the range, the reflection mirror is greatly inclined to the screen 5 for reflecting the beam magnified and projected through the projection lens 3 on the full screen of the screen 5.
Namely, the reflection mirror 4 has a reflection angle corresponding to the angle of magnification and projection of the electron beam, and thereby reflects the magnified and projected electron beam on the full screen of the screen 5. As a result, the mounting position of the screen 5 becomes naturally distant in accordance with the mounting angle of the reflection mirror 4.
Further, owing to the TCL (Total Conjugate Length), which is the projection length of the reflected electron beam, depending on the size of the screen, if large screen for realization is desired, the reflection mirror 4 is required to be more distant from the screen 5 in a distance in order to project the electron beam reflected by the reflection mirror 4 on the full screen of the screen 5.
As a result, because of the distance between the reflection mirror 4 and the screen 5, there is a problem that total width D of the display device 1, that is, the length between the rear of the outer case 6 and surface of the screen 5 becomes so longer than the size of the screen 5 that the compact configuration of the projection display device 1 can not be obtained.
In particular, although the projection display has high quality image and high resolution as compared with PDP TV or LCD TV, the thickness, that is, the total width of the display device becomes lengthened, thus resulting in some problems of the beauty of the device or space application.